The invention relates to a pressure maintenance valve for air spring systems and pneumatic apparatus with a housing to which an air supply line originating from a pump and a pressure relief line are connected.
DE 44 38 192 C2 discloses such a pressure maintenance valve. The pressure maintenance valve is to maintain a certain pressure in a consumer, which generally is permanently connected to a pressure source such as a pump or compressor, at a predetermined minimum value when the pump is switched off or has become inoperative or the pressure of the pressure source has dropped or if the consumer has been separated from the pressure source. The known pressure control valve is at least in part of a hose valve design as it has been used in the past bicycle tubes. A supply line connected to a pump terminates in a valve tube which is surrounded by an elastic rubber hose. In contrast to the bicycle tube valve however the duct line leading to the consumer is symmetrical to the supply duct. Also, the rubber hose is fixed at its opposite ends to the valve tube in a gas tight manner. When the rubber hose is expanded by the pump pressure or the consumer pressure, the valve opens. The open position is the normal position, particularly in pneumatic vehicle spring systems. As a result, the rubber hose acting as a valve member is always in a stretched state so that, in time, it loses the elasticity required for appropriate sealing.
It is the object of the present invention to provide a valve member for a pressure maintenance or control valve, which will securely seal in its closed position, which will remain operative over a long life, which comprises only few parts and which requires no servicing.